1) Field of the Invention
The present invention relates to a high-voltage electric rotating machine.
2) Description of the Related Art
In an electric rotating machine for use in a vehicle, stator windings are accommodated in slots made in a ring-like stator core so that the stator windings partially protrude from the stator core toward the exterior thereof in axial directions, i.e., toward coil end.
In the recent years, to meet the requirements for mounting without changing the volume in an engine room, there is a need to achieve the size reduction and high output of an electric rotating machine including coil ends. For the requirement to reach satisfaction, it can be considered to shorten the distance between the adjacent conductors to the utmost. However, in this case, an extremely large voltage difference occurs between the conductors, which creates a problem in insulating performance.
Concretely, an effective means for this requirement to reach satisfaction is improving the space factor of the windings, and a conventional electric rotating machine employs a technique using conductors (straight-angle lines) each having a rectangular configuration in cross section for stator windings, such as is disclosed in Japanese Patent Laid-Open No. 2000-92766. However, this construction is such that the conductors in a slot are put in phase while the slots adjacent to each other in a circumferential direction take different phases. For higher voltage, in other words, for enhancing the output of the electric rotating machine, an increase in number of turns, i.e., number of conductors in one slot, causes the conductors to overlap more at the coil end section, and when the electric rotating machine is designed to handle a high voltage, this creates a problem in insulating performance between the conductors adjacent to each other. On the other hand, lengthening the distance between the conductors creates a problem of the axial size of the electric rotating machine being enlarged.
For solving the above-mentioned problems, in a conventional electric rotating machine, conductors constituting a specific phase are accommodated in a plurality of slots adjacent to each other in a circumferential direction to increase the number of turns, such as is closed in Japanese Patent Laid-Open No. 2002-228852. This enables increasing the number of turns without increasing the number of poles of the rotor while reducing the number of conductors in one slot to maintain a small outer diameter. Moreover, since there is no need to increase the number of poles of the stator, it is possible to lower the frequency of the stator coil voltage at the same speed of rotation, which enables the reduction of the wiring inductance loss and the inverter switching loss (switching transient loss), thus leading to the improvement of efficiency. Accordingly, this realizes the cost reduction of the inverter and wirings and the reduction of loss and heat generation.
However, in the case of handling a higher voltage, even the construction disclosed in Japanese Patent Laid-Open No. 2002-228852 requires an increase in number of conductors and a reduction of coil ends, which leads to the necessity to shorten the distance between the conductors to the utmost, thereby creating a problem in insulating performance, for that an extremely large voltage difference occurs between the conductors.